Other Middle East and Africa Frequent Flyer Programs - JFK-JNB in SA J; best lounge option for *G

I'm going to be flying JFK-JNB-JFK at the end of next week in J, and am wondering what the best lounge options are in T4. Also, what contract lounge SA uses for it's J customers.

I'll be coming in on the redeye SFO-JFK, and ideally would like to use a lounge with shower facilities.